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Dive into the research topics where Tomoyuki Osaki is active.

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Featured researches published by Tomoyuki Osaki.


Sensors and Actuators B-chemical | 1997

The concentration-estimation of inflammable gases with a semiconductor gas sensor utilizing neural networks and fuzzy inference

Byeongdeok Yea; Tomoyuki Osaki; Kazunori Sugahara; Ryosuke Konishi

This paper proposes a method to estimate the concentration of inflammable gases from transient response patterns which a semiconductor gas sensor shows under periodic heating conditions. The procedure and effectiveness of the method were illustrated for five selected gases of butane, hydrogen, LP gas, methane, and town gas. The response patterns obtained were found to be well reproducible and specific to the kinds of gases. Frequency analysis could be applied easily to the response patterns because of their periodic characteristics, allowing one to extract D.C. and A.C. components of them by fast Fourier transform. The A.C. components remained almost unchanged irrespective of the variations of ambient temperature and/or humidity and gas concentration, proving themselves to be adequate for the concentration-independent discrimination of gases. The D.C. components, on the other hand, depended largely on the variations of gas concentration, being useful for the estimation of gas concentration. It was shown that the discrimination of the five gases supported by a three-layered back propagation neural network as well as the estimation of their concentrations assisted by fuzzy inference were successfully performed.


Sensors and Actuators A-physical | 1994

The discrimination of many kinds of odor species using fuzzy reasoning and neural networks

Byeongdeok Yea; Ryosuke Konishi; Tomoyuki Osaki; Kazunori Sugahara

Abstract To discriminate many kinds of odor species, a system composed of multiple gas sensors and neural networks is proposed. Three commercial gas sensors are used for the system, and four kinds of inflammable gases, four kinds of fragrant smells and one kind of offensive odor are introduced as odor species. The discrimination is performed in two steps to increase the efficiency of the system; the first step is classification of the odor group, that is, the groups of inflammable gases, fragrant smells and offensive odor; the second step is the discrimination of individual odor species in the classified group. 100% group classification rate is obtained by the use of simple fuzzy reasoning and the steady-state response patterns of the sensors. The discrimination of individual odor species is performed with a neural network and transient response patterns of the sensors and a high discrimination rate (99.2%) is achieved.


Applied Surface Science | 1996

Analysis of the sensing mechanism of tin dioxide thin film gas sensors using the change of work function in flammable gas atmosphere

Byeongdeok Yea; Ryosuke Konishi; Tomoyuki Osaki; Satoru Abe; Hiroasa Tanioka; Kazunori Sugahara

Abstract To investigate the sensing mechanism of SnO 2 thin films prepared with the targets-facing type sputtering method, the change of work function of the films was measured with the Kelvin method, and was compared with the change of resistance when they were exposed to hydrogen. The change of work function in the same concentration of hydrogen shows different trends according to the variation of the film temperature and this result reveals that there exist three different models of hydrogen interaction with the film surface or with the oxygen adsorbates on the surface, which depend on the film temperature at that time. The change of resistance of the films shows quick saturation, while that of the work function has trends of slow and continuous decreasing; from these results, it is concluded that the adsorption or desorption of the oxidizing or reducing gases on the film surface are contributed mainly to the change of potential barrier of grain boundaries of the films.


robot and human interactive communication | 2009

Elevator available voice activated wheelchair

Akira Murai; Masaharu Mizuguchi; Takeshi Saitoh; Tomoyuki Osaki; Ryosuke Konishi

This paper develops a new functional voice activated wheelchair. Our system has two major functions. The first function is the collision avoidance function that the wheelchair avoids the wall and obstacle without voice command by using the sensor information. This function has three autonomous movements of the stop movement, avoidance movement and deceleration movement. The second function is the robust elevator entry/exit function which can work smoothly in a variety of situations. Various experiments were carried out and evaluate the proposed system with several conditions. As the result, our system ran indoor environment safely. Furthermore, our system was possible to entry/exit the elevator, and move between floors.


Japanese Journal of Applied Physics | 1999

Investigation of Substrate-dependent Characteristics of SnO2 Thin Films with Hall Effect, X-Ray Diffraction, X-Ray Photoelectron Spectroscopy and Atomic Force Microscopy Measurements

Byeongdeok Yea; Hajime Sasaki; Tomoyuki Osaki; Kazunori Sugahara; Ryosuke Konishi

SnO2 thin films of 100 nm in thickness were prepared on glass and alumina substrates with targets-facing type sputtering apparatus to investigate the substrate-dependent characteristics of the films. The sensitivity of the films is measured in flammable gas atmosphere (hydrogen, butane and methane, 5000 ppm), and it revealed that the SnO2 films on alumina substrates showed better sensitivity for all introduced gases than the films on glass substrates. Hall effect, X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) measurements were performed to clarify the difference of the sensitivity, and it is concluded as follows: 1) The variation of carrier concentration of the films on alumina substrates is larger than those on glass substrates when they are exposed to flammable gases. 2) The structure of the films on alumina substrates is similar to that of SnO2 powder. 3) The film on an alumina substrate contains more oxygen impurities than that on a glass substrate, which can be considered to cause the large variation of carrier concentration. 4) Surface area of the films on alumina substrates is wider than that of the films on glass substrates.


society of instrument and control engineers of japan | 2006

Monocular Autonomy Following Vehicle

Takeshi Saitoh; Tomoyuki Osaki; Ryosuke Konishi

This paper describes the development of the monocular autonomy following vehicle which for reduce a helper burden. The system is composed by a CCD camera, a FPGA board and some control circuits. Our idea is that the distance between the system and the target human is related to the size of the human region in the camera image. Based on this idea, we proposed the automatic human region detection method with S-ACM which is a kind of active contour model. We implemented our method and developed the system. The experiment which followed the target human was done. As the result, we confirmed that the system followed with keeping a fixed distance with the target human


Sensors and Actuators B-chemical | 1999

IMPROVEMENT OF CONCENTRATION-ESTIMATION ALGORITHM FOR INFLAMMABLE GASES UTILIZING FUZZY RULE-BASED NEURAL NETWORKS

Byeongdeok Yea; Tomoyuki Osaki; Kazunori Sugahara; Ryosuke Konishi

Abstract We have proposed an algorithm which can discriminate inflammable gases and estimate their concentration with a semiconductor gas sensor under the periodic operation in our previous paper. In this paper, we propose fuzzy rule-based neural networks, which are composed of two back propagation neural networks, to improve the estimation accuracy and to reduce the time and efforts for creation and tuning of the membership functions. The proposed network is examined in estimating the concentrations of three kinds of inflammable gases, that is, butane, hydrogen and methane, and it is proved that the results are more accurate than those obtained with simplified fuzzy inference.


Japanese Journal of Applied Physics | 1998

Microscopic Analysis of the Degradation Mechanism of Gallium Arsenide Metal-Semiconductor Field-Effect Transistor

Hajime Sasaki; Kazuo Hayashi; Takashi Fujioka; Kiyoshi Mizuguchi; Byeongdeok Yea; Tomoyuki Osaki; Kazunori Sugahara; Ryosuke Konishi

The microscopic degradation mechanism of the recess surface of GaAs metal- semiconductor field-effect transistor (MESFET) after a long duration aging is analyzed using a transmission electron microscope (TEM), Raman scattering and several other analytical methods. Crystallographic arsenic (As) and amorphous gallium (Ga) precipitated after the aging test. Raman scattering during device operation indicates that the temperature of the drain side is higher than that of the source side. Light emission by hot carriers is observed at the drain side of the device during operation. The degradation of the device is accelerated by the hot carriers generated by a thermionic field emission at the high-temperature drain side.


Japanese Journal of Applied Physics | 1998

Light Emission and Surface States Annealing on GaAs Metal Semiconductor Field-Effect Transistor

Hajime Sasaki; Masayuki Abe; Kazuo Hayashi; Takashi Fujioka; Kiyoshi Mizuguchi; Byeongdeok Yea; Tomoyuki Osaki; Kazunori Sugahara; Ryosuke Konishi

The annealing mechanism of surface states in the gallium arsenide metal semiconductor field-effect transistor (GaAs MESFET) is investigated by measuring the light-emission characteristics and excess gate currents generated by hot-carriers. Nonuniform light emission is observed when the Schottky junction is reverse biased, and the nonuniformity is increased with temperature. On the other hand, uniform and strong emission is observed under RF operation even when the device is biased with a deep pinch-off condition. The reverse and forward Schottky current caused by RF swing may not be a main emission mechanism under RF operation. Light emissions due to impact ionization and thermionic field emission are observed separately. The light intensity of the thermionic field emission has a weak temperature coefficient, while that of the impact ionization has a strong negative temperature coefficient. The decreasing rate of the surface states depends on the intensity and the distribution of the light emission during the operation.


Japanese Journal of Applied Physics | 1990

Inverse photoemission spectroscopy study on the oxidation of titanium thin film

Ryosuke Konishi; Satoshi Ikeda; Tomoyuki Osaki; Hiroshi Sasakura

We fabricated an inverse potoemission spectroscopy system of an angle-integrated type. We observed the change in density of unfilled states of evaporated titanium on a polycrystalline Ti substrate. The clean surface spectrum shows a very prominent peak at 0.5 eV above the Fermi level. After 70L, it is considered that the mixed layer of Ti and surface oxide is formed. After 1500L, the spectra which is attibuted. We considered that the stable oxide layer is formed on the surface after 1500L to 50000L.

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Takeshi Saitoh

Kyushu Institute of Technology

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